Electric motor turbine type fuel pumps have been used in automotive engine fuel delivery systems and the like. These pumps typically include a housing adapted to be immersed in a fuel supply tank with an inlet for drawing liquid fuel from the surrounding tank and an outlet for supplying fuel under pressure to the engine. The electric motor drives a pump impeller with an array of circumferentially spaced vanes about the periphery of the impeller. An arcuate pumping channel, with an inlet port and an outlet port at opposed ends surrounds the impeller periphery for developing fuel pressure through a vortex-like action on liquid fuel in pockets formed by the impeller vanes and the surrounding channel. One example of a fuel pump of this type is illustrated in U.S. Pat. No. 5,257,916.
A second example of a fuel pump of this type is disclosed in U.S. Pat. No. 4,591,311, assigned to Nippondenso Co., Ltd. This fuel pump has a discrete, enlarged cross sectional area, low pressure section of its pumping channel which leads to a discrete, high pressure section which has a smaller cross sectional area than the low pressure section. The low pressure section extends less than 180.degree. from the suction port of the pumping channel, and as specifically disclosed, preferably extends through only the first quarter of the pumping channel. Both the high and low pressure sections have constant cross sectional areas throughout their respective arcuate extents. A vapor discharge port communicates with the enlarged low pressure section at its downstream end.
A second type of turbine fuel pump is generally referred to as a side or lateral channel fuel pump. This fuel pump has a rotor with a circumferential array of vanes formed in one face of the rotor and an arcuate pumping channel formed by a groove in a flat face of a stator communicating with the vanes to develop increasing fuel pressure from the inlet port to the outlet port of the pumping channel as the rotor is rotated by an electric motor. One example of a fuel pump of this type is illustrated in U.S. Pat. No. 4,715,777.
Despite significant improvements in the design and construction of turbine type fuel pumps, they are generally very inefficient with an efficiency of generally between about 20% to 45%, and when combined with a typical electric motor having an efficiency of about 45% to 50%, the fuel pumps have an overall efficiency of between about 10% to 15%. Further, it is desirable to reduce the ingestion of vapor into the fuel pump and the amount of vapor discharged from the fuel pump and thus, there is a continuing need to increase the efficiency and vapor handling capabilities of turbine type fuel pumps.